Gunship

A-61 Mantis

The A-61 Mantis Gunship is a staple of the gangs and mercenary groups of Mass Effect 2. It sports a pair of belly-mounted mass accelerator machine guns, and four missile bays over each wing. Its defenses generally consist of just armor plating, but kinetic barriers are not entirely unheard of. 
 

Combine Gunship

The Combine Gunship is an aerial-combat Synth from Half-Life 2, which fires blasts of energy from a pulse cannon to deal with tough ground resistance. The Combine Gunship is part living itself with beige-green coloring and carries no personnel, allowing it to operate off its own instincts and reflexes. It has several external organs, which would appear to used for sensory capabilities and many combine-made add-ons such as jets and a massive propeller in the center of its tail to keep itself afloat. The ideal weapon of choice against them is the RPG, which can take them down in three shots, though if not guided carefully enough the Gunship may shoot them down.